The studies proposed would lay the foundation for understanding the regulation of the cJun kinase and its role in tumorigenesis. Studying the regulation of transcription factor AP-1 will provide clues for understanding the nuclear end of signal transduction cascades from the cell surface and also for understanding the role of AP-1 in the regulation of cell growth; an alternative goal is to study the mechanism of oncogene cooperation and its role in the process and proliferation of tumorigenesis. This proposal connects several central areas of biology such as cellular transformation, oncogene cooperation, transcription control, signal transduction and regulation of cell growth and therefore it would give relevant data for understanding the causes and mechanisms of cancer at the molecular level. As can be seen, this project is closely related to the fields in which I am interested. It is my intention to carry out this work in Dr. M. Karin's lab which is a top level laboratory with a very strong academic environment and with wide experience in molecular biology, oncogene and signal transduction, fields in which Dr. Karin made very important contributions.